Cat extracts may contain pelt, hair, dander, concentrated cat wash, saliva, or any mix of these materials. Due to variability in source material, differences in protein and non-Fel d I allergen levels have been detected. The standardization cat extracts has resulted in the development and implementation of an additional laboratory method and accompanying reference preparations to assist in the characterization of these extracts. The current release test for potency of cat extracts is a radial immunodiffusion test that measures Fel d I content, one of the primary allergens of cat. Blotted RadioImmuno ElectroFocusing (BRIEF) demonstrated the value of simple IsoElectric Focusing (IEF) in the qualitative detection of non-Fel d I allergens in standardized cat extracts. The characterization cat extracts by IEF has proven to be a reliable indicator of clinical activity in patients that are sensitive to non-Fel d I allergens. Activities are in progress to designate standardized cat extracts as cat hair or cat pelt products. Accompanying labeling will indicate the presence of additional non-Fel d I in the pelt products, thereby enhancing the safety of these new products and eliminating confusion related to source material terminology.